Postoperative Insulin Dose for Cardiac Artery Bypass Graft and Other Cardiac Surgeries in Patients with Type 2 Diabetes: A Retrospective Study

Abstract

Purpose: Recommendations on perioperative glycemic control in cardiac surgery are based on coronary artery bypass graft surgery (CABG), though coronary artery disease and valvular disease are pathologically distinct. We aimed to compare the postoperative insulin requirement between CABG and other cardiac surgeries in type 2 diabetic patients and identify predictive factors for the maximum postoperative insulin dose.

Patients and methods: We retrospectively included 60 Japanese patients with diabetes/glucose intolerance (HbA1c > 37 mmol/mol [5.6%]) who were hospitalized for cardiovascular surgery between April 2017 and March 2019. We categorized the subjects into the CABG and non-CABG groups, and performed subgroup analysis on patients who received postoperative insulin therapy.

Results: The CABG group required a significantly higher insulin dose on postoperative days 2, 5, 6, and 7, and a significantly higher maximum postoperative insulin dose (24.6 U vs 9.7 U, P < 0.001) than the non-CABG group. Multivariate linear regression analyses showed that the independent determinants of the maximum postoperative insulin dose were HbA1c and duration of diabetes in the non-CABG group, and HbA1c in the CABG group.

Conclusion: CABG had a higher postoperative insulin requirement than other cardiovascular surgeries; early aggressive insulin therapy is indicated, especially for patients with higher HbA1c levels/longer duration of diabetes.

Keywords: cardiac surgery; coronary artery bypass grafting; insulin dose; postoperative glycemic control; type 2 diabetes.

Figure 1

Inclusion and exclusion flow chart.

Figure 2

The mean glucose level and postoperative insulin dose after surgery in the CABG group and the non-CABG group from postoperative day 1 to postoperative day 7. The black and gray lines represent the mean glucose level in the CABG and non-CABG groups, respectively. On days 5, 6, and 7, the mean glucose level was significantly higher in the CABG group than in the non-CABG group (12.0 mmol/L vs 9.8 mmol/L, P = 0.017; 11.5 mmol/L vs 9.3 mmol/L, P = 0.002; 11.2 mmol/L vs 8.9 mmol/L, P = 0.002). CABG: coronary artery bypass graft. *P < 0.05.

Figure 3

The postoperative insulin dose after surgery in the CABG group and the non-CABG group from postoperative day 1 to postoperative day 7. The black and gray lines represent the postoperative insulin doses for the CABG and non-CABG groups, respectively. On days 2, 5, 6, and 7, the CABG group required a significantly higher insulin dose than the non-CABG group (6.75 U vs 3.11 U, P = 0.048; 12.7 U vs 5.74 U, P = 0.015; 14.3 U vs 5.59 U, P = 0.007; 15.1 U vs 6.19 U, P = 0.015, respectively). CABG: coronary artery bypass graft. (N) The number of patients who received postoperative insulin therapy out of a total of 25 patients in the CABG group and 35 in the non-CABG group. *P < 0.05.